1. Technical Field of the Invention
The invention relates generally to man to machine interfaces (MMIs) implemented using touchscreens; and, more particularly, it relates to a capacitively coupled system.
2. Description of Related Art
The use of MMI systems has been ongoing for some time now. A variety of everyday activities employ some form of MMI. For example, banking may now be performed without the assistance of bank personnel by using an automatic teller machine (ATM); a driver may purchase gasoline without interacting with a sales agent using the interfaces commonly located at the gas pumps. However, these two examples illustrate how the development of rugged MMIs has often taken the route of employing rugged, plastic-type keys located near a display. This has been the industries solution to try to provide a rugged, durable, MMI that is capable of withstanding a variety of environmental and use-induced stresses. Some MMIs do in fact employ a system where a user may make selections by actually touching and interacting with the display itself (in a true touchscreen system), but such applications are not very widespread, and they are nearly never placed in environments where the may the touchscreen is exposed to a rugged environment. These prior art touchscreen systems often find themselves within very environmentally protected installations.
These prior art touchscreen systems typically employ a pattern on a coating that is placed on the surface of the touchscreen that a user does in fact touch. This approach often includes the use of some type of clear coatings over the surface-laid pattern. These patterns are typically very delicate in nature and the engineering required to ensure proper protection of the pattern can be quite extensive, and sometimes very expensive, in some instances. Clearly, the fact that the pattern is placed on the touchscreen surface and is exposed to the environment significantly limits the applications in which many prior art touchscreens may be used. For example, the environmental considerations of humidity, extreme heat and cold (including large and/or rapid temperature changes), and other environmental considerations limit the implementation of such prior art touchscreen technologies.
Many such prior art technologies employ a continuous pattern on the surface of a touchscreen. Oftentimes, the corners of the touchscreen are simultaneously energized with a common signal, and the entire touchscreen surface is energized. When a user touches the surface material, the user's touch interacts with the signals that are provided by the pattern on the surface of a touchscreen. This prior art approach suffers from the fact that the coating is again resident on the surface of the touchscreen where it is exposed to a variety of potentially harmful effects. The degradation of this coating material will degrade the overall performance of the touchscreen system, if not result in the cessation of functionality entirely.
Another prior art employs a matrix type of pattern on the backside of a touchscreen having rows and columns located on the backside of the touchscreen surface that is commonly made up of some protective material. This may be viewed as being a digitally arranged pattern, having discrete rows and columns that may be used as possible touch locations. The system's ability to discern the location of a user's touch is governed by the pre-arranged layout of the matrix type pattern. Employing a row and column design allows the capitalization of information retrieved from the row and column associated with a user's touch. The row and column pattern (on the backside of the surface of the touchscreen) are energized and the associated fields communicatively couple through the protective surface material. The row and column approach typically includes at least one additional layer that separates the rows and columns of the row and column matrix. This additional layer can complicate the touchscreen system, in that, there is yet another layer of material through which signals' communicatively coupling must occur for proper operation and the ability to detect a user's touch.
However, one of the several deficiencies of this approach is inherent to the row and column implementation in terms of resolution and the system's ability to discern the true location of the user's touch. The processing and manufacturing of the system, based on the proximity of the rows and columns, largely governs the resolution of the touchscreen surface. In addition, there is often a limit to the closeness of the proximity of the rows and columns that may be used while still allowing for the signal processing to extract precisely which row and which column is associated with a user's touch. This density into which the rows and columns may be placed also prohibits its implementation into applications of relatively small real estate. Applications that require a relatively small implementation or are extremely real estate/space conscious may not be candidates for this technology. Particularly when these applications require a relatively large number of selectable options on the touchscreen, this particular technology simply cannot meet these needs. The ability of this row and column implementation may, on one hand, enable application in more rugged environments (given that the rows and columns are located on backside layers of the touchscreen); however, on the other hand, this prior art approach fails to meet the needs of other applications (including those requiring higher resolution of selectable options on the touchscreen and/or real estate/space conscious designs).
Moreover, as the closeness of the rows and columns increases, there is ever more cross coupling between them. This may require additional insulating material between them. This may compete with the communicative coupling of the desired signal through the surface's protective material. In addition, the cross coupling between extremely close rows and columns may be so great that the signal processing, absent more advanced and sometimes very complex methods, may simply be unable to discern the true location of a user's touch and to determine its location.
Other prior art technologies are operable to use a pen-like pointer that is used to select portions of a touchscreen. In such implementations, the pen actually interacts with the touchscreen system, in that, the current that travels from the surface of the touchscreen through the pen-like pointer is measured in the calculations that are performed to determine the user's touch location, when the pen-like pointer touches the touchscreen.
Further limitations and disadvantages of conventional and traditional systems will become apparent to one of skill in the art through comparison of such systems with the invention as set forth in the remainder of the present application with reference to the drawings.